What are Boost Controllers?

Boost Controllers are used to control the air pressure delivered to the intake manifold of a turbo-charged engine.  The purpose of which is to regulate this pressure to prevent running the engine above its limits causing possible damage, all the while delivering increased boost power provided by the turbo-charger.

Boost Controllers are merely regulators for the turbo-charged engine.  The installation of which is an enhancement of its original configuration, but it is a modification nonetheless.  Any modification of the engine (or any equipment for that matter), which deviates from the specifications recommended by its manufacturer bring with it the risk of increased wear, which is why any damage brought about by these modifications become the sole responsibility of the owner thereafter.

To understand how boost controllers work, one has to know the difference between a turbo-charged engine and a non turbo-charged engine.  Normally, a non turbo-charged engine system simply takes in the fuel and air mixture into the combustion chamber where it is ignited to produce power and allow the vehicle to run.  The by-product of this process is the exhaust gas, which is normally released into the atmosphere.  A turbo-charged engine makes use of the energy provided by the exhaust gas to force more air into the combustion chamber by the means of a compressor.  The exhaust discharge is connected to a turbine wheel, which turns with the compressor wheel on a common shaft.  The compressor sucks in ambient air and forces it into the intake manifold.  (More fuel is also introduced into the chamber by means of higher volume fuel pumps and high capacity fuel injectors.)  Bigger explosions occur within the combustion chamber producing more power, allowing the engine to run faster than it normally does.  Because the turbo-charger is a closed system in itself, it is very likely that as the RPM goes up, air pressure will continue to build up, and eventually exceed the operating limits of the engine.  For this reason, boost control is needed to protect the engine from damage.

A boost controller is connected to both a source of boost power or charged air (commonly the discharge end of the compressor), and to the wastegate actuator.  Basically it is a valve, which regulates the pressure at which charged air is delivered to the intake manifold by sending part of the charged gas to the wastegate actuator, which in turn opens and closes the wastegate.  The wastegate diverts part of the exhaust gas delivered to the turbine wheel, and in effect regulating its speed.

There are two kinds of MBCs, namely the ball and spring, and the bleeder type.  The difference between the two is the means by which the signal or the excess charged air is sent to the wastegate actuator.  In the case of the ball and spring type MBC, the charged air pressure has to overcome the load of the spring which holds the ball, only then can part of it be sent to the diaphragm of the wastegate actuator to open the waste gate.  Once this excess pressure is released and the speed of the turbine are both regulated, the ball will once again take its place and the MBC will close.  This type of MBC has an adjustor, a control valve that determines how strong the load of the spring will be.  The bleeder type, as its name suggests bleeds part of the boost and sends the rest of it directly to the wastegate actuator.  Similarly, it also has an adjustor which controls how big the leak will be.